A slice of avocado may be the perfect addition to your sandwich, but it can have serious consequences for our feathered and furry friends. According to the ASPCA Animal Poison Control Center in Urbana, IL, pet poisonings from avocado and avocado-based foods like guacamole are a consistent risk. In 2008, the Center managed 115 cases involving ingestions of avocado, and though an overwhelming 83 percent of those incidents involved dogs, the most devastating effects were seen in birds, rabbits and certain large animals like horses and cattle.

A native of Central and South America, avocado (Persea americana) is a subtropical tree that produces a pear-shaped fruit prized for its high fat content, vitamin-rich “meat” and smooth texture. Unfortunately, the fruit also contains a toxin called persin that’s harmful to animals, especially in large quantities.

“Avocado leaves, fruit, seeds and bark all contain the toxic principle known as persin,” says Dana Farbman, CVT, Senior Manager of Professional Communications at APCC. Guatemalan varieties—sold in grocery stores nationwide—are most often involved in pet exposures, Farbman adds, while other strains have varying degrees of toxic potential. Birds—who accounted for 5 percent of avocado cases in 2008—appear to be particularly sensitive to the fatty fruit; consumption can result in respiratory distress, congestion, fluid accumulation around the heart and even death. In curious canines, clinical signs of ingestion can include gastrointestinal distress, vomiting and diarrhea. Typically, these effects are seen in dogs who’ve nibbled on significant amounts of a tree’s fruit or branches.

Pet parents should prevent their animal companions from coming into contact with avocado by placing the fruit—or that festive bowl of guacamole—out of reach. For those lucky Californians who have an avocado tree in their backyards, keep a close eye on your pet when he’s outside, and don’t mistake the toxic fruit for Fido’s gnarly tennis ball.

As always, if you suspect your pet has eaten something toxic, please call your vet or the ASPCA’s 24-hour hotline at (888) 426-4435. For more information about people food that’s toxic for pets, please visit APCC online .